The present invention relates to detection of malfunction during intravenous delivery of fluids and, in particular, it concerns a method and device for detecting malfunction in gravity fed intravenous delivery systems.
It is known a common malfunction encountered in intravenous fluid administration is the infiltration of the fluids into tissues near the tip of the catheter. This phenomenon, variously referred to as “infiltration” and “extravasation”, may occur in a number of different ways. Often it is due to the tip of the catheter penetrating the wall of the vine or artery into which the catheter has been inserted, the tip thereby becoming lodged in the surrounding tissue. Although some texts distinguish between the terms infiltration and extravasation, they are widely used, and will be herein, interchangeably to denote generically any and all circumstances in which intravenous fluid delivery spreads beyond the blood vessel to adjacent tissue. Extravasation may lead to discoloration, discomfort and tissue destruction as well as lack of delivery of the intravenous fluids or drugs into the patient's system. Infiltration of certain drugs into the patient's tissues may be dangerous or cause serious damage, such as necrosis, requiring amputation or other surgical procedures.
Several methods, and device for their implementation, have been proposed for the detection of tissue infiltration during intravenous administration of fluids. One approach is by monitoring the flow rate or pressure of fluid in the tubing supplying the fluid to the catheter. Examples of devices based on such methods are disclosed in U.S. Pat. No. 4,534,756 to Nelson, U.S. Pat. No. 4,784,648 to Singh et al., and U.S. Pat. No. 5,647,853 to Feldmann et al. Commercially available device based on these techniques, however, are generally ineffective since the pressure differences indicative of extravasation are typically small in relation to other causes of pressure variations in an intravenous delivery system during use, such as patient movements or changes in the head pressure of an infusion bag.
A second method for the detection of extravasation is based upon changes in skin temperature in areas where extravasation has occurred. This is due to the temperature deferential between the intravenous fluids and the tissues in which they have accumulated. Examples of these types of devices are described in U.S. Pat. No. 4,010,749 to Shaw and U.S. Pat. No. 4,378,808 to Lichtenstein, which do not work well when the temperature deferential is not significant and false alarms may result from changes in the ambient temperature. Further, devices based on this method, even those that are able to overcome the above-mentioned problems, are intended for the detection of extravasation and are ineffective for detection of other malfunctions.
Additional examples of proposed techniques include measurements of conductivity (e.g. U.S. Pat. No. 5,964,703 to Goodman et al.) and measurements of spectral reflection (e.g. U.S. Pat. No. 4,877,034 to Atkins et al.).
The devices in all of the categories mentioned above suffer from high cost, reliability limitations or complexity of operation. Many of them require calibration before use and the calibrations may be set to accept an inappropriate initial positioning of a catheter thereby allowing extravasation to occur undetected. Thus, the predominant technique for identifying extravasation remains visual inspection by medical personnel of the area surrounding the catheter for swelling or other signs of infiltration. To be effective, this technique requires continual monitoring by trained medical personnel.
It is further known that a number of malfunctions, in addition to extravasation, result in the slowing or total stoppage of the fluid flow in the intravenous delivery system. Methods and devices for monitoring fluid flow include those that monitor flow-rate or pressure such as the devices mentioned above and the device of U.S. Pat. No. 4,816,019 to Kamen, which monitors pressure changes in a negative pressure stepping means. The data generated is processed at compared to data from previous intervals and a predetermine criteria for malfunction. This method, therefore, does not provide an immediate indication of malfunction.
Another method includes devices that count the drops that fall from the fluid bag into the accumulator at the top of the delivery tubing. Variations in that drop-rate are used to determine corresponding variations in the flow-rate of the fluid through the tubing. These devices are susceptible to false indications due to conditions other than malfunction such as change in head pressure in the fluid bag or change of patient position.
There is therefore a need for an accurate, easy to use and inexpensive device and method for continuous monitoring and substantially immediate detection and indication of a malfunction that causes a stoppage or significant slowing in the flow rate in an intravenous delivery system. Especially when the malfunction may be an indication of extravasation of fluid into tissue surrounding the tip of the catheter. It would also be highly advantageous for a device to include components that do not require calibration and would be able to indicate initial malfunction or inappropriate initial placement of the catheter. It would be desirable for components of the device that come in direct contact with the fluid to be disposable components.